Absence of antibodies to cyclic citrullinated peptide in sera of patients and with hepatitis C virus infection cryoglobulinemia

Objective. To determine if antibodies to cyclic citrullinated peptide (anti-CCP) are found in chronic hepatitis C virus (HCV) infection. Methods. Rheumatoid factor (RF) and anti-CCP were measured in sera from 50 patients with HCV infection but without cryoglobulinemia, sera from 29 patients with mixed cryoglobulinemia (including 13 with rheumatic symptoms and 5 with arthritis), and sera from 20 normal blood donors. Anti-CCP was measured by second-generation enzyme-linked immunosorbent assay (ELISA). Results. No sera with elevated anti-CCP were found in patients with HCV infection without cryoglobulinemia, and in that population, the maximum anti-CCP was 10 units, well below the positive cutoff of 20 units. Positive findings on RF testing >13 IU/ml were present in 22 (44%) of the HCV patients, with RF >50 IU/ml in 8 (16%) and a maximum RF of 526 IU/ml. Of the cryoglobulinemia patients, 22 (76%) had positive results on tests for RF, including 18 (62%) with RF >50 IU/ml and a maximum RF of 5,540 IU/ml. Two (6.9%) of the cryoglobulinemia patients had borderline-positive findings on tests for anti-CCP (25 units and 37 units), which were false-positive results caused by nonspecific binding in the ELISA. No association between the RF and the anti-CCP concentrations was found. Conclusion. Whereas RF was frequent in patients with HCV infection with and without cryoglobulinemia, anti-CCP was not observed in patients with uncomplicated HCV infection. Borderline-positive anti-CCP results were observed infrequently in patients with mixed cryoglobulinemia and were caused by nonspecific binding to plastic. Measurement of anti-CCP may help in diagnosing RA in patients with chronic HCV infection.